fix: harden runtime config snapshot publication

backend/test/workspace-runtime-config-lease.test.ts

@@ -1,10 +1,11 @@
 import { test, expect } from "vitest";
 import { chmodSync, existsSync, lstatSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
-import { join } from "node:path";
+import { dirname, join } from "node:path";
 import { execFileSync } from "node:child_process";
 import { createHash } from "node:crypto";
 import { WorkspaceRuntimeConfigLeaseFactory } from "../src/workspaces/runtime-config-lease.js";
+import { parseWorkspaceYaml, serializeWorkspaceYaml } from "../src/workspaces/schema.js";
 
 const workspace = "abc";
 const descriptor = `workspace:
@@ -33,13 +34,14 @@ llm_policy:
 
 function fixture() {
   const root = mkdtempSync(join(tmpdir(), "runtime-config-lease-"));
+  const canonicalDescriptor = serializeWorkspaceYaml(parseWorkspaceYaml(descriptor));
   const snapshots = join(root, "snapshots");
   const repo = join(root, "repo");
   mkdirSync(join(repo, "workspaces"), { recursive: true });
   execFileSync("git", ["init", "--initial-branch=main"], { cwd: repo });
   execFileSync("git", ["config", "user.name", "Fixture"], { cwd: repo });
   execFileSync("git", ["config", "user.email", "fixture@example.invalid"], { cwd: repo });
-  writeFileSync(join(repo, "workspaces", `${workspace}.yaml`), descriptor);
+  writeFileSync(join(repo, "workspaces", `${workspace}.yaml`), canonicalDescriptor);
   execFileSync("git", ["add", "."], { cwd: repo });
   execFileSync("git", ["commit", "-m", "fixture"], { cwd: repo });
   const actualCommit = execFileSync("git", ["rev-parse", "HEAD"], { cwd: repo, encoding: "utf8" }).trim();
@@ -50,17 +52,22 @@ function fixture() {
   const harness = join(root, "harness");
   mkdirSync(snapshotsDir, { recursive: true, mode: 0o700 });
   chmodSync(snapshots, 0o700);
+  const publicFiles = {
+    [`${workspace}.yaml`]: canonicalDescriptor,
+    [`${workspace}.env.example`]: "# fixture\n",
+    [`${workspace}.md`]: "# Lease\n",
+  };
+  for (const [name, contents] of Object.entries(publicFiles)) writeFileSync(join(snapshotsDir, name), contents, { mode: 0o400 });
   writeFileSync(join(snapshotsDir, "snapshot.json"), JSON.stringify({
     head: actualCommit,
     revisions: [{ id: workspace, commit: actualCommit, blob, snapshotPath }],
-    files: { [`${workspace}.yaml`]: createHash("sha256").update(descriptor).digest("hex") },
+    files: Object.fromEntries(Object.entries(publicFiles).map(([name, contents]) => [name, createHash("sha256").update(contents).digest("hex")])),
   }), { mode: 0o400 });
   mkdirSync(harness);
-  writeFileSync(snapshotPath, descriptor, { mode: 0o400 });
   const secret = join(root, "password");
   writeFileSync(secret, "secret", { mode: 0o600 });
   const configPath = join(harness, "config.yaml");
-  writeFileSync(configPath, "profile: test\n");
+  writeFileSync(configPath, "profile: workstation\n");
   const factory = new WorkspaceRuntimeConfigLeaseFactory({
     dataRoot, runtimeSnapshotRoot: snapshots, harnessDir: harness, configPath,
     env: {
@@ -72,7 +79,7 @@ function fixture() {
       internalEmbeddingModel: "qwen3-embedding:0.6b", internalEmbeddingDimensions: 1024,
     },
   });
-  return { root, snapshotPath, factory };
+  return { root, snapshotPath, factory, canonicalDescriptor };
 }
 
 test("session and maintenance share deterministic bytes and path", () => {
@@ -84,6 +91,9 @@ test("session and maintenance share deterministic bytes and path", () => {
     expect(readFileSync(session.path, "utf8")).toBe(readFileSync(maintenance.path, "utf8"));
     expect(lstatSync(session.path).mode & 0o777).toBe(0o400);
     expect(existsSync(maintenance.manifestPath)).toBe(true);
+    const manifest = JSON.parse(readFileSync(maintenance.manifestPath, "utf8"));
+    expect(manifest).toMatchObject({ version: 1, descriptor_dev: expect.any(String), descriptor_ino: expect.any(String) });
+    expect(existsSync(join(dirname(dirname(maintenance.path)), "runtime-config.lock"))).toBe(false);
     session.release(); maintenance.release();
     expect(existsSync(session.path)).toBe(true);
   } finally { rmSync(f.root, { recursive: true, force: true }); }
@@ -100,3 +110,34 @@ test("same revision changed bytes are refused", () => {
     first.release();
   } finally { rmSync(f.root, { recursive: true, force: true }); }
 });
+
+test("snapshot descriptor must equal the Git canonical descriptor", () => {
+  const f = fixture();
+  try {
+    const mutated = f.canonicalDescriptor.replace("database: analytics", "database: evil").replace("name: Lease", "name: Lease analytics");
+    chmodSync(f.snapshotPath, 0o600);
+    writeFileSync(f.snapshotPath, mutated, { mode: 0o600 });
+    chmodSync(f.snapshotPath, 0o400);
+    const manifestPath = join(dirname(f.snapshotPath), "snapshot.json");
+    const manifest = JSON.parse(readFileSync(manifestPath, "utf8"));
+    manifest.files[`${workspace}.yaml`] = createHash("sha256").update(mutated).digest("hex");
+    chmodSync(manifestPath, 0o600);
+    writeFileSync(manifestPath, JSON.stringify(manifest), { mode: 0o600 });
+    chmodSync(manifestPath, 0o400);
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/Git descriptor|integrity|identity/i);
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+test("same-byte replacement of the registry descriptor is refused", () => {
+  const f = fixture();
+  try {
+    const first = f.factory.acquireSession(f.snapshotPath);
+    const replacement = `${f.snapshotPath}.replacement`;
+    writeFileSync(replacement, readFileSync(f.snapshotPath), { mode: 0o400 });
+    chmodSync(f.snapshotPath, 0o600);
+    rmSync(f.snapshotPath);
+    writeFileSync(f.snapshotPath, readFileSync(replacement), { mode: 0o400 });
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/identity|changed|mismatch|trusted/i);
+    first.release();
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});